July 5, 1955
Anal Calcd.: C , 18.0; F, 18.9; I, 63.1. Found: C , 17.9; F , 18.9; I , 61.5. 2. Perfluoropolyphenyl. a. From 1,4-Dibromo-2,3,5,6tetrafluorobenzene .-Equal weights of dibromotetrafluorobenzene5 and activated copper powder (see Kleiderer and Adams*) were mixed thoroughly and sealed in a tube under helium. The tube was heated in a furnace for 80 hours a t 200". After cooling, the tube was opened and the contents extracted with benzene. The benzene solution was poured into ethanol and a white solid precipitated. This solid melted a t 247-260". It was identified as a low polymer containing 18.5% bromine corresponding to Br(CeFd,Br, where n = 4-5. T h e insoluble residue was treated repeatedly with warm nitric acid and concentrated ammonia to remove copper and copper bromide. A light-tan powder remained which contained about 1% of inorganic material. On analysis the compound was found to contain 11.8% bromine, corresponding to n Z 8 . Yo melting point could he obtained upon heating a sample to 360". b . From 1,4-Diiodo-2,3,5,6-tetrafluorobenzene.-Activated copper powder was mixed thoroughly with twice its weight of diiodotetrafluorobenzene in a n open test-tube. This tube was immersed in a n oil-bath and gradually heated to 200' while stirring the contents with a thermometer. A t about 200" the reaction became exothermic and the temperature rose rapidly to 290 O while the material solidified. I t mas then heated for a n additional half-hour a t 250". The solid was removed, crushed and boiled iu benzene. The benzene solution, upon treatment with methanol, yielded only a minute amount of solid. The remaining solid was boiled with pyridine which formed a soluble complex with the copper salt. Subsequently, the solid residue was treated with dilute nitric acid and ammonia, washed with methanol and ether and dried. This sample was analyzed for C , F, and I with the following results: C , 40.6; F, 39.4; I , 14.4. On the basis of the iodine analysis, this indicates n G 10. The purified sample was a grayish powder which could be heated a t 500" in a sealed tube without melting. Some decomposition occurred a t this temperature. as evidenced by the appearance of iodine vapor in the tube, but the bulk of the material remained intact.
Acknowledgments.-The authors gratefully acknowledge the aid of Dr. F. L. 5lohler and hlr. P. Bradt, who performed the mass spectrometer measurements, and Messrs. R. A. Paulson and L. >Iachlan, who performed the chemical analyses.
The half-time of hydrolysis of sarin in the presence of more than thirty hydroxamic acids of a wide variety of structures ranged from about 1 to 7 minutes (2.3 X 10-3 M sarin, 11.5 X lou3 M hydroxamic acid, pH 7.6, 30') as compared with 300 minutes for the spontaneous hydrolysis of sarin. The five most effective hydroxamic acids found, thus far, are sorbhydroxamic acid, p-methoxybenzohydroxamic acid, p-methylbenzohydroxamic acid, dipicolinhydroxamic acid (pyridine-2,6-dihydroxamic acid) and picolinhydroxamic acid, arranged approximately in order of decreasing activity a t pH 7.6. Tables I and I1 list the half-times of the hydrolysis of DFP in the presence of aliphatic, aromatic and heterocyclic hydroxamic acids. TABLE I HYDROLYSIS OF 1 0 - 6 MULEOF D F P MULEo l ~ ACETHYDROXAMIC ACIDSI N 2.2 ML. O F BICARBONATE-COi BUFFER,bH 7.6 AT 38""
+
Acceleration of the Hydrolysis of Organic Fluorophosphates and Fluorophosphonates with Hydroxamic Acids BY B. E. HACKLEY, JR., R. PLAPINGER, M. STOLBERG AND T. WAGNER-JAUREGG 28, 1955 RECEIVEDFEBRUARY
Wilson and Meislichl reported that acetylcholinesterase inhibited by diisopropyl fluorophosphate (DFP) can be reactivated in the presence of nicotinhydroxamic acid methiodide. It had been observed previously in this Laboratory that certain hydroxamic acids (RCONHOH) at a QH of 7.5 and higher, strongly accelerate the hydrolysis of diisopropyl phosphorofluoridate2and of isopropyl methylphosphonofluoridate (sarin). Since the enzyme reactivation reaction and the hydrolysis reaction may be based on a similar principle and their comparison may help to obtain more information about their mechanism, we wish to report briefly some of otir experiments. u. Wilson and E. K . Xleislich, T H I SJ O U R N A L , 76, 4698 (1953) ( 2 ) This is the new name for diisoprolJyl fliiorophosphate, as pruposed I)? llir Anieric:iii Cliriiiiv:rl S o c i e i y ; ( ' ~ F , I I . n i i g . . V r w s , 38, 151 I (l!l,72j. (1) I
Moles of acid (as Cot) produced per mole of DFP a t t h e end of reacn
Half-time of hydrolysis, min.
D F P alone 2500-3000 2 acethydroxamic acid 36 1.9 DFP DFP aminoacethydroxamic acid 29 1.8 DFP 3-pyridylacethydroxamic acid 23 2.0 The rates of hydrolysis were determined maiiometricall!r as described in earlier papers.324~5
+ + +
TABLE I1 HYDROLYSIS OF 57.5 X MOLEOF D F P 287.5 X MOLE OF BENZOHYDROXAMIC ACID AXD ITS PYRIDINE ANALOGSI N 34 ML. O F 0.1 KC1 A 1 DH 7.6 AND 30""
+
(8) E. C. Kleiderer a n d R. Adams, THISJ O U R N A L , 66, 4219 (1933).
~VASHISGTON, D. C .
3651
NOTES
Half-time of hydrolysis
Moles of acid produced per mole of DFP a t end of reacn.
D F P alone Several days 2 DFP benzohydroxatnic acid 22 min. 2.2 2.2 D F P nicotinhydroxamic acid 20 min. D F P nicotinhydroxamic acid methiodide 68 min. 0 ,ti DFP picolinhydroxamic acid 20 min. 2.0 DFP picolinhydroxamic acid methiodide 65 miti. C) . 3 isonicotinhydroxamic DFP acid 28 min. 2.2 DFP isoniotinhydroxamic acid methiodide 73 min. 0.4 a A Beckman automatic titrator was used in these experiments for the determination of the acid produced during the hydrolysis.
+ + + + + + +
From the figures in Table I it can be seen that introduction of an amino or a pyridino group into the a-position of acethydroxamic acid leads only to slightly increased reactivity with DFP. When a pyridine nucleus is substituted for the phenyl group in benzohydroxamic acid the differences in the observed half-times are even less (Table 11). (3) B. J. Jandorf, 1'.\Vaytler-Jaurrgg, J . J . O'Neill a n d 11,Slolberg. THISJ O U R N A L 74, , 1691 (1Y;Z). (4) T. \Vaguer-Jnuregg and E. I?. IIackley, J r . , ibiel , 76, 212: (1953) ( 5 ) ' 1 ~ . \VV;iynPr-J:iiirrgy, 1 3 . l i l r w k l c v , I r . , C L ( I / . , iiii,! , 77, !I? ( I !lSLij,
3ti52
VOl. 77
I\;OTES
Quaternization of the nitrogen in pyridinehydroxThe same product (11) also can be obtained by amic acids decreased the reactivity markedly. the reaction of benzohydroxamic acid with benzeneHowever, since only 0.3-0.6 mole of acid was ti- sulfonyl c h l ~ r i d e instead ~ ~ ' ~ of D F P or sarin, and trable with these substances it seems questionable the mechanism of the reaction is identical with all whether the half-times observed in these cases are three reagents. directly comparable with the other values.6 With p-methylbenz:)-, p-nitrobenzo-, p y a n o The rate of reaction between D F P or sarin arid benzo-, picolin- and nicotinhydroxamic acids and hydroxamic acids becomes much faster with in- sarin, reaction products analogous to O-phenylcarcreasing pH of the solution. This demonstrates bamyl benzohydroxamate (11) were obtained. that probably the hydroxamic acid anion is the Other hydroxamic acids probably follow the s a i i i c reactive form. The common hydroxainic acids are pathway of reaction. weakly acidic. We determined the pKa'sof fifteen of Several hydroxyamidines, Re(-")"OH, the hydroxamic acids which reacted rapidly with which are the imino analogs of hydroxamic acids, sarin and found values approximately between 7.8 have been found t o react with D F P or sarin, aland 9.3. Two cyclic hydroxamic acids of structure X7 though much slower than the corresponding hyand BS with a pKa of 5.7 and 6.4, respectively, re- droxamic acids. I n this case stable phosphorylation products could be isolated and will be described o in a later publication. The reactivation of DFP-inactivated cholinester . ase by hydroxamic acids might be visualized as a transfer of the phosphoryl group to the hydroxamic acid, with subsequent rearrangement of the hypoOH thetical phosphorylated hydroxamic acid, thus B ChE-P(O)(OR)z KCONHOH + ChE f Racted only at a very slow rate with DFP. The rela- CONHOP(0)(0R)z (unstable). There is as yet no tion between the acidity of the hydroxamic acids experimental proof for this assumption. and their reactivity with phosphoro- and with Experimental phosphonofluoridates will be more extensively discussed in later publications. A . Compounds Investigated.-The liydroxaniic acid5 Approximately two moles of acid is formed dur- used in this study were for the most part synthesized in thii iiig the reactions reported in Table I and I1 which is Laboratory. A few were obtained commercially, and somc samples werc received as a result of rcquests from outsidc indicative of hydrolysis of D F P with formation of agencies (see Aclino;vledgments). HF and HOPO(OR)z. In experiments with benzoIn general, the hydrosamic acids were prepared by standhydroxamic acid, nicotinhydroxamic acid and pico- ard procedures from the corresponding carboxylic esters 01' linhydroxamic acid, using the reaction conditions acid chlorides by reaction n-ith hydrosylamine.il Th? \c acids which are water soluble usually were 150described in Table 11, it was found that 1.5 to 2 hydroxamic lated as their relatively insoluble cupric salts. Treatment moles of hydroxamic acid disappeared during the with hydrogen sulfide reinnved the copper as copper sulfidc reaction. This demonstrates that the hydroxamic and yielded the free hydroxainic acid. p-Aminobenzohydrosamic acid v.as ,.btained from / I acids are not true catalysts in the hydrolysis reacnitrobenzohydroxamic acid by catalytic reduction in akohiJ1 tion inasmuch as they undergo traiisfoririatinIi. ~ r i t hplatinum oxide a t room temperature. The reaction product between D F P or sarin The methiodides were prepared by rcflusing the Iiydro < and benzohydroxamic acid has been isolated and amic acid in 95% ethanol for 4 hours with a 100% excess n f identified as 0-phenylcarbamyl benzohydroxa- methyl iodide, and were isolated by standard tecliniquc,. The reaction of picolinhydroxamic acid with methyl iodidc mate, C6H5CONHOCONHC& (11). The reac- gave poor yields of the desired product together with small tion mechanism probably involves the preliminary amounts of a byproduct. phosphmylation of the hydroxamate ion by D F P or Table 111 contains physical and analytical data on / I by sarin. The unstable phosphorylation product substituted benzohydroxanlic acids most of which have n q t been characterized previously. In Table IV the correspond(I), which never could be isolated, undergoes a Los- ing data are listed for several heterocyclic hydroxamic acid., sen rearrangement to give the hydrolyzed D F P or B. Reaction of Hydroxamic Acids with DFP or with sarin and phenyl isocyanate, which reacts with Sarin.-This reaction ivas carried out in a similar niant1c.r more hydroxamic acid to give the final isolated as described for benzenesulfonpl chloride in an earlier pap The products obtained are listed in Table V. product (TI) Decomposition (in some cases with shrinking and brov I I -
+
PhCOSIlOH
+ FP(O)(OR), = PhCOKHOP(O)(OR)2 ( I ) f HF I --+ PhNCO + HOP(O)(OR)I
(1) (2 ) P h S C O t PhCOIiHOH = PhCOSHOCOSHPh( 11) (3)
2PhCOSHOI-I f FP(O)(OR)Z = PhCOSHOCOSHPh (11) HF ~-
+
+ HOP(O)(OR)? (1 + 2 + 3
( 0 ) T h e ratio of the hali-times lor the reaction of 1 0 - 0 mole of DFP with 5 X 10-6 mole of nicotitlhydroxamic acid a n d its methiodide, respectivelv. in 1)irarbonate h a f f e r under the conditions of Table I i r a ~ iurinrl t o l ~ enii;~~r,xtmately 1 : :. 1.2 mt,lrc of acid was protlitcr, l2!18 ( l $ j 5 2 ) . i b ) .\, I 0 r i l i ~ ) r u. i i i d K l l r l l l r r , F;vr , 36, 3ti.50 (1902).
ing, in others with melting and evolution of gas bubble 1 probably occurs a t the temperature at which carbon dioxi I C is liberated, with formation of the corresponding N,S'diarylurea: RCOXHOCONHR = (RNH)L!O j-Coz. The second decomposition (melting) points (in Table 1. given in parentheses) are rather close to the melting points of the corresponding diary1 ureas, except in the case of t h c ptiitrophenyl derivative (the decomposition point of ",E'~
(9) M. Stolberg, R . Tweit. G . R I . Steinberg a n d T. Wagner-Jauregi: Trixs JOURNAL. 77, 765 (195;). (10) C. D. H u r d a n d L. Daurr, ibid., 76, 2791 (19Sd). (11) Review artirles: H. L. Yale, Chem. Reus., 33, 209 (1943); i'. Rfathis, Buli. so
